Semiconductor device and fabrication method thereof

ABSTRACT

The present disclosure provides a semiconductor device and a fabrication method. The method includes: providing a substrate and forming initial fins on the substrate. The initial fins include a sacrificial material layer and a first material layer on the sacrificial material layer, first trenches are formed between adjacent initial fins, and the first trenches expose the substrate. A first layer is formed in the first trenches. Second trenches are formed in the initial fins. The second trenches expose the substrate, the sacrificial material layer is formed into a sacrificial fin layer, the first material layer is formed into fins, and the fins are located on the sacrificial fin layer. The sacrificial fin layer is removed to form first fin openings between the substrate and the fins. An isolation structure is formed on the substrate and in the first fin openings.

CROSS-REFERENCES TO RELATED APPLICATION

This application claims the priority of Chinese Patent Application No.201910097624.2, filed on Jan. 31, 2019, the content of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to the field of semiconductormanufacturing and, in particular, to a semiconductor device and afabrication method thereof.

BACKGROUND

With rapid development of semiconductor manufacturing technologies,semiconductor devices are moving in a direction toward higher componentdensities and higher integration. Semiconductor devices, as the mostbasic devices, are widely used. A traditional planar device has weakcontrol of a channel current, resulting in short-channel effects and aleakage current, which ultimately affects electrical performance of asemiconductor device.

To overcome the short-channel effects of a device and suppress theleakage current, a conventional method proposes a fin field effecttransistor (Fin FET), which is a common multi-gate device, andstructures of the Fin FET include fins and an isolation layer on asurface of a semiconductor substrate, that the isolation layer covers aportion of sidewalls of the fins, and a surface of the isolation layeris lower than a top of the fins; gate structures on the surface of theisolation layer, and the top and the side walls of the fins; and sourceand drain regions in the fins on both sides of the gate structures. Thegate structures of the Fin FET has a weak control ability on the finscovered by the isolation structure, especially a bottom of the finscovered by the isolation structure, and a leakage current of an offstate of the semiconductor device is difficult to control. To reduce theleakage current of the off state of the Fin FET, SOI(Silicon-On-Insulator) technology can be used.

However, there is a need to improve performance of the semiconductordevice fabricated by the conventional methods.

SUMMARY

One aspect of the present disclosure provides a fabrication method of asemiconductor device, including: providing a substrate; forming initialfins on the substrate, that the initial fins include a sacrificialmaterial layer and a first material layer on a surface of thesacrificial material layer, first trenches are formed between adjacentinitial fins, and a bottom of the first trenches exposes the substrate;forming a first layer in the first trenches; forming second trenches inthe initial fins, that a bottom of the second trenches exposes thesubstrate, the sacrificial material layer between the second trenchesand the first trenches is formed into a sacrificial fin layer, the firstmaterial layer between the second trenches and the first trenches isformed into fins, and the fins are located on a surface of thesacrificial fin layer; removing the sacrificial fin layer to form firstfin openings between the substrate and the fins; and forming anisolation structure on the substrate and in the first fin openings.

Another aspect of the present disclosure provides a semiconductordevice, including: a substrate, including protrusions; fins formed overthe substrate and aligned with the protrusions, wherein orthographicprojections of a fin and a protrusion on the substrate coincide witheach other; and an isolation structure, formed on the substrate andbetween the protrusions and the fins.

Other aspects or embodiments of the present disclosure can be understoodby those skilled in the art in light of the description, the claims, andthe drawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are merely examples for illustrative purposesaccording to various disclosed embodiments and are not intended to limitthe scope of the present disclosure.

FIGS. 1 to 9 illustrate structures corresponding to certain stagesduring an exemplary fabrication process of a semiconductor deviceconsistent with various disclosed embodiments of the present disclosure;and

FIG. 10 illustrates an exemplary fabrication process of a semiconductordevice consistent with various disclosed embodiments of the presentdisclosure.

DETAILED DESCRIPTION

A semiconductor device is often formed by: providing a SOI substrate,that the SOI substrate includes a silicon substrate, an insulating oxidelayer on a surface of the silicon substrate, and a monocrystallinesilicon layer on a surface of the insulating oxide layer; and etchingthe monocrystalline silicon layer on the SOI to form fins.

The conventional method for fabricating the SOI substrate is to implanta buried oxide layer in the silicon substrate, which is a complicatedprocess and has high costs, thereby restricting development of thesemiconductor device on the SOI substrate.

In a fabricating method provided by the present disclosure, by forminginitial fins on a substrate, that the initial fins include a sacrificialmaterial layer and a first material layer on a surface of thesacrificial material layer; forming second trenches in the initial finsto form fins and a sacrificial fin layer; removing the sacrificial finlayer to form first fin openings between the substrate and the fins; andforming an isolation structure on the substrate and in the first finopenings, a silicon semiconductor device on an insulating substrate isfabricated. The method improves the performance of the semiconductordevice.

The above described objects, features and advantages of the presentdisclosure may become easier to be understood from the embodiments ofthe present disclosure described in detail below with reference to theaccompanying drawings.

FIGS. 1 to 9 illustrate structures corresponding to certain stagesduring an exemplary fabrication process of a semiconductor deviceconsistent with various disclosed embodiments of the present disclosure.

FIG. 10 illustrates an exemplary fabrication process of a semiconductordevice consistent with various disclosed embodiments of the presentdisclosure.

Referring to FIG. 1 and FIG. 10, a substrate 100 is provided (S01).

The substrate 100 is made of monocrystalline silicon. The substrate 100may also be made of one of polysilicon and amorphous silicon. Thesubstrate 100 may also be made of a semiconductor material such as oneof germanium, silicon germanium, gallium arsenide, and the like.

In one embodiment, the substrate 100 is made of monocrystalline silicon.

An initial sacrificial material layer 101 is formed on the substrate100, and the initial sacrificial material layer 101 and the substrate100 are made of different materials.

The initial sacrificial material layer 101 is made of silicon germanium.The initial sacrificial material layer 101 may also be made of asemiconductor material such as one of germanium, silicon germanium,gallium arsenide, and the like.

The initial sacrificial material layer 101 provides a space forsubsequent formation of first fin openings.

In one embodiment, the initial sacrificial material layer 101 is made ofsilicon germanium.

An initial first material layer 102 is formed on the initial sacrificialmaterial layer 101, and the initial first material layer 102 and theinitial sacrificial material layer 101 are made of different materials.

The initial first material layer 102 is made of monocrystalline silicon.The initial first material layer 102 may also be made of one ofpolysilicon and amorphous silicon. The initial first material layer 102may also be made of a semiconductor material such as one of germanium,silicon germanium, gallium arsenide, and the like.

The initial first material layer 102 provides a material layer forsubsequent formation of fins.

In one embodiment, the initial first material layer 102 and thesubstrate 100 are made of a same material. The initial first materiallayer 102 is made of monocrystalline silicon.

In other embodiments, the initial first material layer 102 and thesubstrate 100 may be made of different materials.

In one embodiment, the method further includes: forming an initialprotective layer 103 on a surface of the initial first material layer102.

The initial protective layer 103 provides a material layer forsubsequent formation of a protective layer.

The initial first material layer 102 and the initial sacrificialmaterial layer 101 are etched to form initial fins with first trenchesbetween adjacent initial fins, that a bottom of the first trenchesexposes the substrate 100.

Referring to FIG. 2, a first auxiliary pattern layer 104 is formed onthe initial first material layer 102, that the first auxiliary patternlayer 104 covers a portion of a surface of the initial first materiallayer 102. A first mask layer 105 is formed on sidewalls of the firstauxiliary pattern layer 104.

The first auxiliary pattern layer 104 provides assistance for formingthe first mask layer 105, and the first auxiliary pattern layer 104 andthe first mask layer 105 determine positions and shapes of the initialfins that are subsequently formed.

A distance between adjacent first auxiliary pattern layers 104 is equal.

A method for forming the first auxiliary pattern layer 104 includes:forming a first auxiliary pattern film (not shown) on the initial firstmaterial layer 102; forming a first pattern layer (not shown) on asurface of the first auxiliary pattern film, that the first patternlayer exposes a portion of a surface of the first auxiliary patternfilm; and etching the first auxiliary pattern film by using the firstpattern layer as a mask until a surface of the initial first material102 is exposed, to form the first auxiliary pattern layer 104 on thesurface of the initial first material layer 102.

In one embodiment, a first auxiliary pattern film is formed on a surfaceof the initial protection layer 103. The first auxiliary pattern film isetched by using a first pattern layer as a mask until a surface of theinitial protection layer 103 is exposed, to form the first auxiliarypattern layer 104 on the surface of the initial protective layer 103.

The first auxiliary pattern layer 104 may be made of one of amorphouscarbon and amorphous silicon.

In one embodiment, the first auxiliary pattern layer 104 is made ofamorphous carbon.

A first mask layer 105 determines positions and shapes of the fins.

A method for forming the first mask layer 105 includes: forming aninitial first mask layer (not shown) on a surface of the initial firstmaterial layer 102, that the initial first mask layer covers a top andsidewalls of the first auxiliary pattern layer 104; and etching back theinitial first mask layer to expose the top of the first auxiliarypattern layer 104, to form the first mask layer 105 on the sidewalls ofthe first auxiliary pattern layer 104.

The first mask layer 105 may be made of one of silicon nitride, siliconoxide, silicon oxynitride, silicon borohydride, silicon oxynitride, andsilicon oxynitride.

In one embodiment, the first mask layer 105 is made of silicon nitride.

In another embodiment, after a first mask layer is formed, a firstauxiliary pattern layer is removed. A method for forming initial finsincludes: after the first mask layer is formed, before the firstauxiliary pattern layer is removed, by using the first auxiliary patternlayer and the first mask layer as masks, etching an initial firstmaterial layer and an initial sacrificial material layer to form theinitial fins on a substrate, that first trenches are formed betweenadjacent initial fins, and a bottom of the first trenches exposes thesubstrate.

Referring to FIG. 3 and FIG. 10 (S02), after the first mask layer 105 isformed, the initial first material layer 102 and the initial sacrificialmaterial layer 101 are etched by using the first auxiliary pattern layer104 and the first mask layer 105 as masks, to form initial fins on thesubstrate, that first trenches 130 are formed between adjacent initialfins, and a bottom of the first trenches 130 exposes the substrate 100.

The initial first material layer 102 and the initial sacrificialmaterial layer 101 are etched such that the initial first material layer102 is formed into a first material layer 112, and the initialsacrificial material layer 101 is formed into a sacrificial materiallayer 111. The initial fins include the sacrificial material layer 111and the first material layer 112 on the sacrificial material layer 111.

A thickness of the sacrificial material layer 111 is about 5 nm to about100 nm.

The first trenches 130 expose sidewalls of the initial fins.

A process of etching the initial first material layer 102 and theinitial sacrificial material layer 101 includes an anisotropic dryetching.

In one embodiment, the initial first material layer 102, the initialsacrificial material layer 101, and a portion of the substrate 100 areetched to form the initial fins.

Referring to FIG. 4, after the initial fins are formed, a portion of thesacrificial material layer 111 of the initial fins exposed by the firsttrenches 130 is removed, to form second fin openings 140 intocorresponding sidewalls of the first trenches 130 and, between the firstmaterial layer 112 and the substrate 100.

The portion of the sacrificial material layer 111 of the initial finsexposed by the first trenches 130 is removed such that the sacrificialmaterial layer 111 is formed into a first sacrificial layer 121, andsidewalls of the first sacrificial layer 121 are recessed relative tothe first material layer 112 of the initial fins.

The second fin openings 140 provide a space for subsequent formation ofan isolation structure.

A process of removing a portion of the sacrificial material layer 111 ofthe initial fins exposed by the first trenches 130 is a wet etchingprocess. A solution of the wet etching process for removing a portion ofthe sacrificial material layer 111 has a good selection ratio of siliconand silicon germanium, and can ensure that the silicon morphology is notaffected while removing the silicon germanium. Parameters of the wetetching process for removing a portion of the sacrificial material layer111 in one embodiment include: a HCl gas solution as an etchingsolution, a temperature between about 25 degrees Celsius to about 300degrees Celsius, and a volume percentage of the HCl gas solution betweenabout 20% to about 90%.

In one embodiment, the sacrificial material layer 111 is made ofsilicon, the first material layer 112 is made of silicon germanium, andan etching solution with HCl has a good selection ratio.

In another embodiment, second fin openings are not formed.

Referring to FIG. 5 and FIG. 10, a first layer 150 is formed in thefirst trenches 130 (S03).

The first layer 150 is made of one of silicon oxide, silicon nitride,silicon oxynitride, silicon borohydride, silicon oxynitride, and siliconoxynitride.

In one embodiment, the first layer 150 is made of silicon oxide.

In one embodiment, the method further includes forming the first layer150 in the second fin openings 140.

A method of forming the first layer 150 includes forming a firstisolation film (not shown) on the substrate 100 and in the firsttrenches 130 to cover the initial fins; and etching back the firstisolation film, to form the first layer 150.

A process of forming the first isolation film is a deposition processsuch as a fluid chemical vapor deposition process. The first isolationfilm is formed by the fluid chemical vapor deposition process, so thatfilling performance of the first isolation film is better.

The first layer 150 provides a material layer for subsequent formationof an isolation structure.

A subsequent removal of a sacrificial fin layer 131 forms first finopenings between fins 122 and the substrate 100, and the first layer 150supports the fins 122.

In another embodiment, a first layer serves as a sacrificial layer, andthe first layer is made of one of SiC and GaAs.

Referring to FIG. 6, after the first layer 150 is formed, the firstauxiliary pattern layer 104 is removed to expose a portion of a surfaceof the initial fins. Referring to FIG. 6, after the first auxiliarypattern layer 104 is removed, the initial fins are etched by using thefirst mask layer 105 as a mask, to form second trenches 160 in theinitial fins, that a bottom of the second trenches 160 exposes thesubstrate 100. As such, the second trench 160 may pass through the firstmaterial layer 112 and first sacrificial layer 121 and into thesubstrate 100, to form fins 122 (from the first material layer 112) anda sacrificial fin layer 131 (from the first sacrificial layer 121). Thefins 122 are formed on the sacrificial fin layer 131 (S04).

The second trenches 160 expose sidewalls of the fins 122. Thesacrificial fin layer 131 is located between the substrate 100 and thefins 122.

In another embodiment, second fin openings may not be formed, secondtrenches are formed in initial fins, a bottom of the second trenchesexposes the substrate, such that a sacrificial material layer betweenthe second trenches and first trenches is formed into a sacrificial finlayer, and a first material layer between the second trenches and thefirst trenches is formed into fins that are on a surface of thesacrificial fin layer.

A process of etching the first material layer 112 of the initial finsand the first sacrificial layer 121 of the initial fins includes ananisotropic dry etching.

In another embodiment, a method of forming second trenches includes:after a first layer is formed, forming a second mask layer on a surfaceof initial fins, that the second mask layer exposes a portion of thesurface of the initial fins; and etching the initial fins by using thesecond mask layer as a mask to form the second trenches on a substrate.

Referring to FIG. 7 and FIG. 10, after the second trenches 160 areformed, the sacrificial fin layer 131 is removed to form first finopenings 170 (S05).

Alternatively, the sacrificial fin layer 131 exposed by the secondtrenches 160 is removed to form the first fin openings 170.

The first fin openings 170 provide a space for subsequent formation ofan isolation structure.

In one embodiment, after the sacrificial fin layer 131 is removed, themethod further includes: removing the first mask layer 105 at a top ofthe fins 122.

After the first mask layer 105 on the top of the fins 122 is removed, aprotective layer 123 on the top of the fins 122 is exposed.

In other embodiments, the first mask layer on the top of the fins 122 isremoved before the sacrificial fin layer 131 is removed.

Referring to FIG. 10, the isolation structure is formed on the substrate100 and in the first fin openings 170 (S06).

In one embodiment, the isolation structure covers a portion of sidewallsof the fins 122.

Referring to FIG. 8, after the fins 122 are formed and the first masklayer 105 is removed, a first isolation layer 151 is formed in thesecond trenches 160 and in the first fin openings 170.

A method of forming the first isolation layer 151 includes: forming asecond isolation film (not shown) on the substrate 100, in the secondtrenches 160, and in the first fin openings 170, to cover the fins 122;and planarizing the second isolation film until a top of the fins 122 isexposed to form the first isolation layer 151.

In one embodiment, the first isolation layer 151 exposes a surface ofthe protective layer 123.

A process of forming a second isolation film is a deposition processsuch as a fluid chemical vapor deposition process. A second isolationfilm formed by the fluid chemical vapor deposition process has betterfilling performance.

The first isolation layer 151 provides a material layer for subsequentlyforming an isolation structure.

Referring to FIG. 9, after the first isolation layer 151 is formed, thefirst layer 150 and the first isolation layer 151 are etched back toform an isolation structure 153, that the isolation structure 153 coversa portion of the sidewalls of the fins 122, and the isolation structure153 fills the first fin openings 170.

A top surface of the isolation structure 153 is higher than a bottomsurface of the fins 122.

The isolation structure 153 is formed between the fins 122 and thesubstrate 100. The fins 122, the isolation structure 153, and thesubstrate 100 form a silicon structure on an insulating substrate. Thesilicon structure on the insulating substrate is formed on aconventional single-material substrate; therefore cost is low, because asingle-material substrate is inexpensive. Moreover, the siliconstructure on the insulating substrate is well integrated with otherprocesses.

In another embodiment, a first layer is used as a sacrificial layer, anda method for forming an isolation structure includes: after fins areformed, forming a first isolation layer in second trenches and first finopenings; after the first isolation layer is formed, removing the firstlayer, exposing first trenches, and forming a second isolation layer inthe first trenches; after the second isolation layer is formed, etchingback the second isolation layer and the first isolation layer to formthe isolation structure.

Correspondingly, one embodiment further provides a semiconductor deviceformed by the above method. Referring to FIG. 9, the semiconductordevice includes: a substrate 100; fins 122 on the substrate 100, thatfirst fin openings are formed between the fins 122 and the substrate100; and an isolation structure 153 on the substrate 100, that theisolation structure 153 covers a portion of sidewall of the fins 122,and the isolation structure 153 fills the first fin openings.

Compared to the conventional fabrication methods, the technical solutionof embodiments of the present disclosure has the following beneficialeffects.

In the fabrication method of a semiconductor device provided by thepresent disclosure, a first layer is formed in first trenches, and thefirst layer supports fins after removing a sacrificial fin layer. Firstfin openings are located between a substrate and the fins, and anisolation structure is formed on the substrate and in the first finopenings. Having the isolation structure between the fins and thesubstrate, the fins, the isolation structure, and the substrate form asilicon structure on an insulating substrate. The silicon structure onthe insulating substrate is formed on a conventional single-materialsubstrate, therefore cost is low, because a single-material substrate isinexpensive. Moreover, the silicon structure on the insulating substrateis well integrated with other processes.

The embodiments disclosed herein are exemplary only. Other applications,advantages, alternations, modifications, or equivalents to the disclosedembodiments that are obvious to those skilled in the art are intended tobe encompassed within the scope of the present disclosure.

What is claimed is:
 1. A fabrication method of a semiconductor device,comprising: providing a substrate; forming initial fins on thesubstrate, wherein the initial fins include a sacrificial material layerand a first material layer on a surface of the sacrificial materiallayer, first trenches are formed between adjacent initial fins, and abottom of the first trenches exposes the substrate; forming a firstlayer in the first trenches; forming second trenches in the initialfins, wherein a bottom of the second trenches exposes the substrate, thesacrificial material layer between the second trenches and the firsttrenches is formed into a sacrificial fin layer, the first materiallayer between the second trenches and the first trenches is formed intofins, and the fins are located on a surface of the sacrificial finlayer; removing the sacrificial fin layer to form first fin openingsbetween the substrate and the fins, and forming an isolation structureon the substrate and in the first fin openings.
 2. The method accordingto claim 1, wherein forming the initial fins on the substrate includes:forming an initial sacrificial material layer on the substrate, whereinthe initial sacrificial material layer and the substrate are made ofdifferent materials; forming an initial first material layer on theinitial sacrificial material layer, wherein the initial first materiallayer and the initial sacrificial material layer are made of differentmaterials; and etching the initial first material layer and the initialsacrificial material layer, to form the initial fins on the substrate,such that, the initial first material layer is formed into the firstmaterial layer, and the initial sacrificial material layer is formedinto the sacrificial material layer.
 3. The method according to claim 2,wherein etching the initial first material layer and the initialsacrificial material layer includes: forming a first auxiliary patternlayer on the initial first material layer, wherein the first auxiliarypattern layer covers a portion of a surface of the initial firstmaterial layer; forming a first mask layer on sidewalls of the firstauxiliary pattern layer; and by using the first auxiliary pattern layerand the first mask layer as masks, etching the initial first materiallayer and the initial sacrificial material layer, to form the initialfins on the substrate, such that, the initial first material layer isformed into the first material layer, and the initial sacrificialmaterial layer is formed into the sacrificial material layer.
 4. Themethod according to claim 3, wherein forming the first mask layerincludes: forming an initial first mask layer on a surface of theinitial first material layer, wherein the initial first mask layercovers a top and the sidewalls of the first auxiliary pattern layer; andetching back the initial first mask layer to expose the top of the firstauxiliary pattern layer, and form the first mask layer on the sidewallsof the first auxiliary pattern layer.
 5. The method according to claim3, wherein forming the second trenches includes: after the first layeris formed, removing the first auxiliary pattern layer to expose aportion of a surface of the initial fins; and after the first auxiliarypattern layer is removed, etching the initial fins to form the secondtrenches by using the first mask layer as a mask.
 6. The methodaccording to claim 2, wherein: the initial first material layer is madeof a same material as the substrate.
 7. The method according to one ofclaims 1 and 6, wherein: the substrate is made of monocrystallinesilicon.
 8. The method according to claim 7, wherein: the initialsacrificial material layer is made of silicon germanium.
 9. The methodaccording to claim 1, wherein: a thickness of the sacrificial materiallayer is about 5 nm to about 100 nm.
 10. The method according to claim1, wherein forming the second trenches includes: forming a second masklayer on a surface of the initial fins, wherein the second mask layerexposes a portion of the surface of the initial fins; and etching theinitial fins to form the second trenches in the initial fins, by usingthe second mask layer as a mask.
 11. The method according to claim 3,wherein: the first mask layer is made of one of silicon nitride, siliconoxide, silicon oxynitride, silicon borohydride, silicon oxynitride, andsilicon oxynitride.
 12. The method according to claim 3, wherein: thefirst auxiliary pattern layer is made of one of amorphous carbon andamorphous silicon.
 13. The method according to claim 1, wherein: thefirst layer is made of one of SiC and GaAs.
 14. The method according toclaim 13, wherein forming the isolation structure includes: forming afirst isolation layer in the second trenches and the first fin openings;after the first isolation layer is formed, removing the first layer,exposing the first trenches, and forming a second isolation layer in thefirst trenches; and after the second isolation layer is formed, etchingback the second isolation layer and the first isolation layer to formthe isolation structure.
 15. The method according to claim 1, wherein:the first layer is made of one of silicon oxide, silicon nitride,silicon oxynitride, silicon borohydride, silicon oxynitride, and siliconoxynitride.
 16. The method according to claim 15, wherein forming theisolation structure includes: forming a first isolation layer in thesecond trenches and the first fin openings; after the first isolationlayer is formed, etching back the first layer and the first isolationlayer to form the isolation structure, wherein the isolation structurefills the first fin openings.
 17. The method according to claim 1,further comprising: after the initial fins are formed, and before thefirst layer is formed, removing a portion of the sacrificial materiallayer in the initial fins exposed by the first trenches, to form secondfin openings recessed into corresponding sidewalls of the firsttrenches, thereby forming a first sacrificial layer from the sacrificialmaterial layer, wherein: the second trenches in the initial fins areformed through the first sacrificial layer, leaving portions of thefirst sacrificial layer between the second trenches and the firsttrenches as the sacrificial fin layer.
 18. A semiconductor device,comprising: a substrate, including protrusions; fins formed over thesubstrate and aligned with the protrusions, wherein orthographicprojections of a fin and a protrusion on the substrate coincide witheach other; and an isolation structure, formed on the substrate andbetween the protrusions and the fins.
 19. The device according to claim18, wherein: the substrate is made of monocrystalline silicon.
 20. Thedevice according to claim 18, wherein: the isolation structure is madeof one of silicon oxide, silicon nitride, silicon oxynitride, siliconborohydride, silicon oxynitride, and silicon oxynitride.